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Jackie Kennedy
Credit: Tom Wargacki/Getty

As Jacqueline Kennedy Onassis' live-in assistant and sometime nanny between 1964 and 1977, a young Kathy McKeon got to know the former first lady on an intimate, personal level. With that closeness came rare access to Jackie’s “jam-packed” walk-in closet in her apartment at 1040 Fifth Avenue in New York City.

McKeon, now a 72-year-old grandmother of six, reveals new details about Jackie and children Caroline and John Jr. in her upcoming memoir, Jackie’s Girl, due out May 9 and excerpted in this week’s issue of PEOPLE.

One of McKeon’s jobs as personal assistant to Jackie – or “Madam,” as the staff called her – was to prepare and care for the former first lady’s wardrobe, which overflowed with clothes and shoes from luxury stores like Bergdorf Goodman and Saks Fifth Avenue.

Jackie Kennedy at Airport
Credit: Getty

“The bedroom walk-in closet was jam-packed with Madam’s everyday clothing, all arranged according to color,” McKeon writes in her memoir. “I had never seen such a dazzling selection of shoes! London-look boots, pumps in every color, spotless sneakers for morning jogs around the reservoir.”

VIDEO: The Most Expensive Shoes You Can Buy

But her shoes betrayed a little-known secret about the woman viewed by many admirers as the picture of effortless perfection.

McKeon reveals: “More intriguing to me was the quarter-inch lift affixed to one heel on each pair of shoes, apparently meant to compensate for one leg being slightly shorter than the other. No one would have ever guessed.”

Jackie's Girl Book Cover

McKeon, who was 19 years old and had recently emigrated from Ireland when she began working for the Kennedys, grew very close to Jackie over the 13 years she spent working for the former first lady.

Even after McKeon married (in a wedding attended by Jackie, Caroline and John Jr.) and left to raise her own three children, the Kennedy family invited her and her kids to their Hyannis Port, Massachusetts, home every summer.

“[Jackie] was more than this glamorous figure,” McKeon tells PEOPLE. “She made me feel like part of the family.” For more from McKeon on Jackie’s life after JFK, check out this week’s issue.

Also on sale now: PEOPLE’s commemorative edition Jack & Jackie: Remembering Camelot.

This article originally appeared on People.com.

This Story Originally Appeared On People